1. Field of the Invention
The present disclosure relates to a method for forming a pattern of a hole or trench on a substrate, and more specifically, to a method for forming a hole or trench by using double patterning technology with directed self-assembly (DSA) material.
2. Description of the Prior Art
As semiconductor devices become smaller and highly integrated, the whole chip area is increased in proportion to an increase in memory capacity. However, an area of a cell region in the semiconductor device, which contains patterns, is practically decreased. A pitch size of patterns, for example a critical dimension (CD) of a pattern or distance between two adjacent patterns, becomes reduced. With high integration of semiconductor devices, a technology for processing semiconductor devices in a finer manner has been needed. As a technology for providing fine patterns for semiconductor devices, a method of forming a resist pattern using a photolithographic process and etching a base film using the resist pattern as a mask has been commonly used.
As a design rule of semiconductor devices is decreased, the pitch size of patterns which is realized in the semiconductor devices becomes reduced. Making semiconductor devices fine beyond the resolution limit of a photolithographic process has been desired. However, since the maximum resolution of a photolithography apparatus is preset, it is difficult to form patterns that are finer than the maximum resolution of the apparatus. For example, it has been said that the resolution of ArF (193 nm) immersion exposure, which has been widely used in exposure technology, may reach a limit of 4× nm generations.
In order to further proceed to a finer 3X nm generation, a double patterning technology such as a lithography etching lithography etching (LELE) process or the like has been actively developed. For example, a process is known in which a first resist opening pattern of a first resist film is formed and a first hole or trench pattern is formed on a base film using the formed first resist opening pattern, and, subsequently, a second resist opening pattern of a second resist film is formed and a second hole or trench pattern is formed on the base film using the formed second resist opening pattern.
In the development of various double patterning technology, US patent application publication, US 2011/0124196, provides a novel method exclusively for forming contact hole array pattern with fine pitch smaller than 40 nm. This method uses the double patterning scheme of uniformly-disposed pillar cores and an atomic deposition layer (ALD) layer conformally-deposited on the pillar cores to define the whole contact holes array with desired pitch. However, the utmost issue of this double patterning scheme is that the defined hole patterns will have two different shapes. This inbuilt feature would significantly impact CD uniformity of the hole pattern.
Accordingly, there is a demand for a method for forming a contact hole pattern array with better CD uniformity.